Various types of disease conditions present clinical situations in which a vessel of a patient needs to be artificially supported to maintain an open passageway through which fluids, such as blood, can flow. For example, blood flow through an artery can be impeded due to a build-up of cholesterol on the interior wall of the vessel. Also, vessel walls can be weakened by a variety of conditions, such of aneurysms.
Intraluminal support frames provide an artificial mechanism to support a body vessel. The prior art provides many examples of intraluminal support frames, including an array of cardiovascular stents. Many prior art support frames are tubular-shaped members that are placed in the lumen of the vessel and, once deployed, exert a radially-outward directed force onto the vessel wall to provide the desired support. Support frames can also provide a base architecture onto which additional functionality can be built. For example, graft members and valve members can be attached to a support frame to provide graft and valve devices, respectively. The support frame in these types of devices can serve simply to provide the base architecture, or to both provide the base architecture and a vessel support mechanism as described above.
Intraluminal support frames are typically positioned at a point of treatment in a body vessel by navigation through the vessel, and possibly other connected vessels, until the point of treatment is reached. This navigation requires that the support frame be able to move axially through the vessel(s) while still maintaining the ability to exert an outward force on the interior wall once deployed. Accordingly, intraluminal support frames typically have radially unexpanded and expanded configurations. In the unexpanded configuration, the support frame has a relatively small diameter that allows it to be moved axially through the vessel. In the expanded configuration, the support frame has a relatively large diameter that allows it to engage an interior wall of the body vessel and exert a radially outward directed force on the interior wall, thereby providing the desired support to the vessel.
Once the support frame is navigated to a desired point of treatment in a body vessel, the support frame is deployed by allowing it to assume its expanded diameter. During expansion from the radially unexpanded configuration to the radially expanded configuration, intraluminal support frames can exhibit a degree of foreshortening, which can affect the accuracy of placement of the support frame. Indeed, the foreshortening effect is frequently referred to as a “jumping” of the support frame during deployment. Foreshortening is particularly evident in self-expandable support frames, which do not require an application of force to achieve the expanded configuration. Foreshortening of support frames in a medical device that includes an additional component or components, such as a graft member or a valve member, could have an effect on the functioning of the component(s).